Pull up WithT interface allowing for overrides (#1172)

i18next · Jan 17, 2019 · 140934b · 140934b
1 parent 0c60262
commit 140934b
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Showing 2 changed files with 43 additions and 10 deletions.
diff --git a/index.d.ts b/index.d.ts
@@ -468,6 +468,17 @@ declare namespace i18next {
     (key: TKeys | TKeys[], options?: TranslationOptions<TValues>): TResult
   }
 
+  /**
+     * WARNING: Order with generic type parametes are defferent from TranslationFunction for usability
+     * see: https://github.com/i18next/react-i18next/issues/662
+   */
+  interface WithT{
+    /**
+     * Please have a look at the translation functions like interpolation, formatting and plurals for more details on using it.
+     */
+    t<TKeys extends string = string, TValues extends object = object, TResult = any> (key: TKeys | TKeys[], options?: TranslationOptions<TValues>) : TResult;
+  }
+
   interface Resource {
     [language: string]: ResourceLanguage
   }
@@ -566,7 +577,7 @@ declare namespace i18next {
     error(...args: any[]): void
   }
 
-  interface i18n {
+  interface i18n extends WithT {
     /**
      * The default export of the i18next module is an i18next instance ready to be initialized by calling init.
      * You can create additional instances using the createInstance function.
@@ -590,11 +601,6 @@ declare namespace i18next {
      */
     services: Services
 
-    /**
-     * Please have a look at the translation functions like interpolation, formatting and plurals for more details on using it.
-     */
-    t: TranslationFunction
-
     /**
      * Uses the same resolve functionality as the t function and returns true if a key exists.
      */

diff --git a/test/typescript/i18next-tests.ts b/test/typescript/i18next-tests.ts
@@ -520,7 +520,34 @@ const t4: i18next.TranslationFunction<string, object, KeyList> = (
   options?: i18next.TranslationOptions,
 ) => ''
 
-i18next.exists('friend')
-i18next.exists(['friend', 'tree'])
-i18next.exists('friend', { myVar: 'someValue' })
-i18next.exists(['friend', 'tree'], { myVar: 'someValue' })
+i18next.exists('friend');
+i18next.exists(['friend', 'tree']);
+i18next.exists('friend', { myVar: 'someValue' });
+i18next.exists(['friend', 'tree'], { myVar: 'someValue' });
+
+i18next.t<KeyList>("friend", { myVar: "someValue" });
+i18next.t<KeyList>(["friend", "tree"], { myVar: "someValue" });
+i18next.t<KeyList, {myVar: "someValue"}>("friend", { myVar: "someValue" });
+i18next.t<KeyList, {myVar: "someValue"}>(["friend", "tree"], { myVar: "someValue" });
+
+// NOTION: disable no-unnecessary-generics for generic pattern test.
+/* tslint:disable:no-unnecessary-generics */
+interface ExWithT extends i18next.WithT {
+  t<Keys extends KeyList= KeyList, Val extends object= object, R= string>(keys: Keys|Keys[], options?: i18next.TranslationOptions<Val>): R;
+  t<Keys extends OtherKeyList= OtherKeyList, Val extends object= object, R= string>(keys: Keys|Keys[], options?: i18next.TranslationOptions<Val>): R;
+  t<Keys extends string= KeyList, R= string>(keys: Keys|Keys[]): R;
+}
+
+type OtherKeyList = "private" | "public";
+
+(i18next as ExWithT).t("friend");
+(i18next as ExWithT).t("tree");
+(i18next as ExWithT).t("private");
+(i18next as ExWithT).t("public");
+(i18next as ExWithT).t("friend", {});
+(i18next as ExWithT).t("private", {});
+(i18next as ExWithT).t<KeyList, {myVar: "someValue"}>("friend", {myVar: "someValue"});
+(i18next as ExWithT).t<OtherKeyList, {myVar: "someValue"}>("private", {myVar: "someValue"});
+const result = (i18next as ExWithT).t<KeyList, {myVar: "someValue"}, {result: 'result'}>("friend", {myVar: "someValue"});
+type Check<T extends {result: 'result'}> = T;
+type ExWithTResult = Check<typeof result>;